You are correct, one could debate this forever. I've known pilots of both and each swore by what they flew to the exclusion of everything else. I knew a physician from New Zealand who flew P-51s and after the war built a 2/3 scale model of one.

But they were different airplanes. The P-47 was almost a single-engine bomber with an incredible munitions load. The P-51 was a pure fighter. While both of them were capable of ground support and attack as well as dogfights, it's a bit like comparing pickup trucks with 2-seat sport cars. They'll both get you there, it's what you want to do along the way.